[vsnet-grb-info 18931] GRB 170111A: Swift-XRT refined Analysis
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Thu Jan 12 02:54:36 JST 2017
TITLE: GCN CIRCULAR
NUMBER: 20431
SUBJECT: GRB 170111A: Swift-XRT refined Analysis
DATE: 17/01/11 17:52:10 GMT
FROM: Phil Evans at U of Leicester <pae9 at leicester.ac.uk>
P.A. Evans (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A.
Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU),
T.G.R. Roegiers (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U.
Leicester) and report on behalf of the Swift-XRT team: report on
behalf of the Swift-XRT team:
We have analysed 6.2 ks of XRT data for GRB 170111A, from 96 s to 42.0
ks after the BAT trigger. The data comprise 17 s in Windowed Timing
(WT) mode (the first 4 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+5.1 ks) can be modelled with a
power-law decay with a decay index of alpha=0.72 (+/-0.18).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.68 (+0.17, -0.16). The
best-fitting absorption column is 3.6 (+0.9, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 3.1 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.6 x 10^-11 (6.1 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.6 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 3.1 x 10^20 cm^-2
Excess significance: 6.6 sigma
Photon index: 1.68 (+0.17, -0.16)
If the light curve continues to decay with a power-law decay index of
0.72, the count rate at T+24 hours will be 0.020 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.5 x
10^-13 (1.2 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00731887.
This circular is an official product of the Swift-XRT team.
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